Reflow soldering apparatus and method

Abstract

The present invention provides an apparatus and a method for operating reflow soldering in a mounting field whereby an abnormality in transfer of circuit boards can be detected with high reliability. Whether or not a circuit board is transferred by a transfer conveyor is judged. A discharge conveyor is started when a control device judges occurrence of transfer abnormality. After the discharge conveyor starts, the transfer abnormality is determined to be a drop of the circuit board if a discharge completion detector detects that a dropped circuit board is discharged. And then the control device continues the reflow soldering. The transfer abnormality in the reflow soldering apparatus can be detected with high reliability because it can be detected whether the transfer abnormality is either the drop or a clog of the circuit board.

What is claimed is:  
     
       1. A reflow soldering method comprising: 
       judging whether or not a circuit board with electronic components mounted thereon is transferred by a transfer conveyor from an entrance to an exit of a reflow soldering apparatus with a heating furnace for operating reflow soldering to the electronic components on the circuit board by passing the circuit board through the heating furnace;  
       detecting, when presence of transfer abnormality is judged, whether or not a dropped circuit board dropped from the transfer conveyor while being transferred by the transfer conveyor is discharged to an outside of the apparatus by a discharge conveyor arranged below the transfer conveyor;  
       determining, when the dropped circuit board is detected to be discharged by the discharge conveyor, that the transfer abnormality is the drop of the circuit board; and  
       continuing the operation of the reflow soldering.  
     
     
       2. The reflow soldering method according to  claim 1 , wherein, when a plurality of circuit boards are carried to the entrance in a single line, in the determination of the transfer abnormality, the transfer abnormality is determined as a jam of the circuit boards at the transfer conveyor and a temperature of the heating furnace is lowered unless the dropped circuit board is detected to be discharged and also unless the circuit board is detected to be discharged by the transfer conveyor at the exit. 
     
     
       3. The reflow soldering method according to  claim 1 , wherein in the judgement of the circuit board transfer, the presence or absence of the transfer abnormality is judged on a basis of whether or not the discharge of the circuit board is detected within a circuit board detect time after a transfer estimate time has passed; the circuit board detect time corresponding to a passing time of the circuit board in a transfer direction of the circuit board, and the transfer estimate time being a time required for the circuit board to be transferred from the entrance to the exit. 
     
     
       4. The reflow soldering method according to  claim 2 , wherein in the judgement of the circuit board transfer, the presence or absence of the transfer abnormality is judged on a basis of whether or not the discharge of the circuit board is detected within a circuit board detect time after a transfer estimate time has passed; the circuit board detect time corresponding to a passing time of the circuit board in a transfer direction of the circuit board, and the transfer estimate time being a time required for the circuit board to be transferred from the entrance to the exit. 
     
     
       5. The reflow soldering method according to  claim 1 , wherein, when a plurality of circuit boards are carried to the entrance in a single line, in the judgement of the circuit board transfer, the presence or absence of the transfer abnormality is judged on a basis of a comparison between a carry-in interval of circuit boards carried adjacently to the entrance and a discharge interval of the adjacent circuit boards discharged from the exit. 
     
     
       6. The reflow soldering method according to  claim 2 , wherein, when a plurality of circuit boards are carried to the entrance in a single line, in the judgement of the circuit board transfer, the presence or absence of the transfer abnormality is judged on a basis of a comparison between a carry-in interval of circuit boards carried adjacently to the entrance and a discharge interval of the adjacent circuit boards discharged from the exit. 
     
     
       7. The reflow soldering method according to  claim 1 , wherein in the judgement of the circuit board transfer, the presence or absence of the transfer abnormality is judged on a basis of a comparison between a circuit board count set value and a count value, the circuit board count set value corresponding to the number of circuit boards which can be presented on the transfer conveyor between the entrance and the exit, and the count value corresponding to the number of circuit boards actually present on the transfer conveyor between the entrance and the exit. 
     
     
       8. The reflow soldering method according to  claim 2 , wherein in the judgement of the circuit board transfer, the presence or absence of the transfer abnormality is judged on a basis of a comparison between a circuit board count set value and a count value, the circuit board count set value corresponding to the number of circuit boards which can be presented on the transfer conveyor between the entrance and the exit, and the count value corresponding to the number of circuit boards actually present on the transfer conveyor between the entrance and the exit.